U.S. patent application number 13/319130 was filed with the patent office on 2012-03-22 for threated connection for drilling and operating hydrocarbon wells.
This patent application is currently assigned to SUMITOMO METAL INDUSTRIES, LTD.. Invention is credited to Olivier Caron, Scott Granger, Eric Verger.
Application Number | 20120068458 13/319130 |
Document ID | / |
Family ID | 41348704 |
Filed Date | 2012-03-22 |
United States Patent
Application |
20120068458 |
Kind Code |
A1 |
Granger; Scott ; et
al. |
March 22, 2012 |
THREATED CONNECTION FOR DRILLING AND OPERATING HYDROCARBON
WELLS
Abstract
A set for manufacturing a threaded connection, including first
and second tubular components with an axis of revolution, one of
their ends including a threaded zone formed on the external or
internal peripheral surface of the component depending on whether
the threaded end is of male or female type, the ends finishing in a
terminal surface. The threaded zones include, over at least a
portion, threads including, viewed in longitudinal section passing
through the axis of revolution of the tubular components, a thread
crest, a thread root, a load flank, and a stabbing flank, the width
of the thread crests of each tubular component reducing in the
direction of the terminal surface of the tubular component under
consideration, while the width of the thread roots increases,
profiles of the load flanks and/or the stabbing flanks of the male
and female threaded zones, viewed in longitudinal section passing
through the axis of revolution of the tubular components, each
having at least one identical portion such that the male and female
threads can be fitted one into the other over the identical
portions when the first and second tubular components are made up
one into the other. The identical portions of the male and female
ends are radially offset with respect to each other.
Inventors: |
Granger; Scott;
(Valenciennes, FR) ; Caron; Olivier; (Ramecourt,
FR) ; Verger; Eric; (Gommegnies, FR) |
Assignee: |
SUMITOMO METAL INDUSTRIES,
LTD.
Osaka-Shi, Osaka
JP
VALLOUREC MANNESMANN OIL & GAS FRANCE
Aulnoye-Aymeries
FR
|
Family ID: |
41348704 |
Appl. No.: |
13/319130 |
Filed: |
May 7, 2010 |
PCT Filed: |
May 7, 2010 |
PCT NO: |
PCT/EP2010/002805 |
371 Date: |
November 17, 2011 |
Current U.S.
Class: |
285/334 ;
285/390 |
Current CPC
Class: |
E21B 17/042 20130101;
E21B 17/0423 20130101 |
Class at
Publication: |
285/334 ;
285/390 |
International
Class: |
F16L 15/06 20060101
F16L015/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2009 |
FR |
0902497 |
Claims
1-14. (canceled)
15: A set for manufacturing a threaded connection, comprising: a
first and a second tubular component with an axis of revolution,
one of their ends including a threaded zone formed on an external
or internal peripheral surface of the component depending on
whether the threaded end is of male or female type, the ends
finishing in a terminal surface, the threaded zones comprising,
over at least a portion, threads comprising, viewed in longitudinal
section passing through the axis of revolution of the tubular
components, a thread crest, a thread root, a load flank, and a
stabbing flank, the width of the thread crests of each tubular
component reducing in the direction of the terminal surface of the
tubular component under consideration, while the width of the
thread roots increases, profiles of the load flanks and/or the
stabbing flanks of the male and female threaded zones, viewed in
longitudinal section passing through the axis of revolution of the
tubular components, each having at least one identical portion such
that the male and female threads can be fitted one into the other
over the identical portions when the first and second tubular
components are made up one into the other, wherein the identical
portions of the male and female ends are radially offset with
respect to each other.
16: A set for manufacturing a threaded connection according to
claim 15, wherein the distance of the portion of the load flanks
and/or the stabbing flanks of the male threaded zone from the axis
of revolution is smaller than the distance of the corresponding
portion of the corresponding flanks of the female threaded zone
from the axis of revolution.
17: A set for manufacturing a threaded connection according to
claim 15, wherein the distance of the portion of the load flanks
and/or the stabbing flanks of the male threaded zone from the axis
of revolution is greater than the distance of the corresponding
portion of the corresponding flanks of the female threaded zone
from the axis of revolution.
18: A set for manufacturing a threaded connection according to
claim 15, wherein the distance of the portion of the load flanks
and/or the stabbing flanks of the male threaded zone from the axis
of revolution differs from the distance of the portion of the
corresponding flanks of the female threaded zone from the axis of
revolution by a value in a range of 0.01 to 0.05 mm.
19: A set for manufacturing a threaded connection according to
claim 18, wherein the distance of the portion of the load flanks
and/or the stabbing flanks of the male threaded zone from the axis
of revolution differs from the distance of the portion of the
corresponding flanks of the female threaded zone from the axis of
revolution by a value substantially equal to 0.02 mm.
20: A set for manufacturing a threaded connection according to
claim 15, wherein the portions of the load flanks and/or the
stabbing flanks of the male and female threaded zones are
constituted by two segments connected together tangentially via a
first radius of curvature.
21: A set for manufacturing a threaded connection according to
claim 20, wherein the two segments connected together tangentially
via a radius of curvature form an angle in a range 90 to 120
degrees.
22: A set for manufacturing a threaded connection according to
claim 15, wherein the identical portions of the load flanks and/or
the stabbing flanks of the male and female threaded zones are
connected to the thread crest and/or root by a second radius of
curvature.
23: A set for manufacturing a threaded connection according to
claim 15, wherein the at least one fitting portion of the load
flanks and/or stabbing flanks of the male and female threaded zones
is a continuous curve including a point of inflection, the curve
being connected tangentially to the crest and to the root of the
thread.
24: A set for manufacturing a threaded connection according to
claim 15, wherein the threaded zones each include a taper
generatrix forming an angle with the axis of revolution of the
tubular components.
25: A set for manufacturing a threaded connection according to
claim 15, wherein the thread crests and roots are parallel to the
axis of the tubular component.
26: A threaded connection resulting from connecting a set in
accordance with claim 15.
27: A threaded connection according to claim 26, wherein the male
and female ends each respectively comprise a sealing surface, each
sealing surface configured to cooperate in tightening contact with
each other when the portions of the threaded zones cooperate
following self-locking make-up.
28: A threaded connection according to claim 26, wherein the
threaded connection is a threaded connection of a drilling
component.
Description
[0001] The present invention relates to a set for manufacturing a
threaded connection used for drilling and operating hydrocarbon
wells, the set comprising a first and a second tubular component,
one being provided with a male type threaded end and the other
being provided with a female type threaded end, the two ends being
capable of cooperating by self-locking make-up. The invention also
relates to a threaded connection resulting from connecting two
tubular components by make-up.
[0002] The term "component used for drilling and operating
hydrocarbon wells" means any element with a substantially tubular
shape intended to be connected to another element of the same type
or not in order when complete to constitute either a string for
drilling a hydrocarbon well or a riser for maintenance such as a
work over riser, or for operation such as a production riser, or a
casing string or a tubing string involved in operating a well. The
invention is of particular application to components used in a
drill string such as drill pipes, heavy weight drill pipes, drill
collars and the parts which connect pipes and heavy weight pipes
known as tool joints.
[0003] In known manner, each component used in a drill string
generally comprises an end provided with a male threaded zone
and/or an end provided with a female threaded zone each intended to
be connected by make-up with the corresponding end of another
component, the assembly defining a connection. The string
constituted thereby is driven from the surface of the well in
rotation during drilling; for this reason, the components have to
be made up together to a high torque in order to be able to
transmit a rotational torque which is sufficient to allow drilling
of the well to be carried out without break-out or even
over-torquing.
[0004] In conventional products, the make-up torque is generally
achieved thanks to cooperation by tightening of abutment surfaces
provided on each of the components which are intended to be made
up. However, because of the fact that the extent of the abutment
surfaces is a fraction of the thickness of the tubes, the critical
plastification threshold of the abutment surfaces is reached
rapidly when too high a make-up torque is applied.
[0005] For this reason, threadings have been developed which can
relieve the abutment surfaces of at least a portion or even all of
the loads which they are not capable of taking up. The aim was
achieved by using self-locking threadings such as those described
in the prior art document US Re 30 647 and US Re 34 467. In this
type of self-locking threads, the flanks of the threads (also
termed teeth) of the male end and the flanks of the threads (also
termed teeth) of the female end have a constant lead but the thread
widths are variable.
[0006] More precisely, the widths of the thread crests (or teeth)
increase progressively for the threads of the male end,
respectively the female end, with distance from the male end,
respectively from the female end. Thus, during make-up the male and
female threads (or teeth) finish up locking into each other in a
position corresponding to a locking point. More precisely, locking
occurs for self-locking threadings when the flanks of the male
threads (or teeth) lock against the flanks of the corresponding
female threads (or teeth). When the locking position is reached,
the male and female threaded zones made up into each other have a
plane of symmetry along which the widths at the common mid-height
of the male and female teeth located at the end of the male
threaded zone corresponds to the widths at the common mid-height of
the male and female teeth located at the end of the female threaded
zone.
[0007] For this reason, the make-up torque is taken up by all of
the contact surfaces between the flanks, i.e. a total surface area
which is much larger than that constituted by the abutment surfaces
of the prior art.
[0008] In order to reinforce the interlock of the male threads with
the female threads, the male and female threads (or teeth) usually
have a generally dovetail profile so that they are solidly fitted
one inside the other after make-up. This dovetail configuration
means that risks of jump-out, corresponding to the male and female
threads coming apart when the threaded zones are made up into each
other, are avoided. More precisely, the geometry of dovetail
threads increases the radial rigidity of their connection compared
with "trapezoidal" threads as defined in API5B, where the axial
width reduces from the base of the thread to the thread crest, and
compared with "triangular" threads such as those defined in
API7.
[0009] Further, because of the ever-increasing challenges as
regards tightness to fluid, a reinforced degree of tightness,
corresponding to high pressures at the threaded connection between
two tubular components, must be guaranteed. To this end, in
addition to the thread flanks ensuring the tighteness, it is known
to bring the thread crests and roots into tightening contact. Thus,
the tightness is provided between the interior of the connection
and the exterior of the connection at the threading per se.
[0010] However, the dovetail configuration suffers from several
disadvantages when the thread crests and roots are brought into
tightening contact during make-up. The fact that the thread flanks
make a negative angle with the axis that passes through the thread
roots (i.e. an angle which is the inverse of that used in the case
of a trapezoidal thread configuration) increases the risks of the
male and female threads galling when making up and breaking out a
connection. This means that make-up progress is difficult and
reduces the fatigue strength of the threads.
[0011] In order to overcome this problem, several documents such as
U.S. Pat. No. 6,254,146, U.S. Pat. No. 4,600,024 and WO-2008/039317
propose a flank configuration using facets in order to reduce the
contact pressure between the thread crests and thread roots during
make-up. For this reason, the threads have a generally dovetail
profile while reducing the surface area of the thread roots and
thread crests. However, that configuration does not solve the
problems of contact between the thread crests and roots to a
sufficient extent.
[0012] For this reason, the aim of the invention is to conserve
minimized contact pressures between the thread crests and thread
roots during the make-up operation in order to guard against the
problems of galling and to guarantee at the end of make-up (i.e.
during the tightening operation which concludes connection) a high
contact pressure between the thread crests and roots. This high
contact pressure enables in particular to increase the tightness of
the connection.
[0013] More precisely, the invention concerns a set for
manufacturing a threaded connection, comprising a first and a
second tubular component each with an axis of revolution, one of
their ends being provided with a threaded zone formed on the
external or internal peripheral surface of the component depending
on whether the threaded end is of the male or female type, said
ends finishing in a terminal surface, said threaded zones
comprising, over at least a portion, threads comprising, viewed in
longitudinal section passing through the axis of revolution of the
tubular components, a thread crest, a thread root, a load flank and
a stabbing flank, the width of the thread crests of each tubular
component reducing in the direction of the terminal surface of the
tubular component under consideration, while the width of the
thread roots increases, the profiles of the load flanks and/or the
stabbing flanks of the male and female threaded zones, viewed in
longitudinal section passing through the axis of revolution of the
tubular components, each having at least one identical portion such
that the male and female threads can be fitted one into the other
over said identical portions when the first and second tubular
components are made up one into the other, characterized in that
the identical portions of the male and female ends are radially
offset with respect to each other.
[0014] Optional complementary or substitutional features of the
invention are described below.
[0015] The distance of the identical portion of the profile of the
load flanks and/or the stabbing flanks of the male threaded zone
from the axis of revolution is smaller than the distance of the
identical portion of the corresponding profile of the load flanks
and/or the stabbing flanks of the female threaded zone from the
axis of revolution.
[0016] The distance of the identical portion of the profile of the
load flanks and/or the stabbing flanks of the male threaded zone
from the axis of revolution is greater than the distance of the
identical portion of the corresponding profile of the load flanks
and/or the stabbing flanks of the female threaded zone from the
axis of revolution.
[0017] The distance of the portion of the load flanks and/or the
stabbing flanks of the male threaded zone from the axis of
revolution differs from the distance of the corresponding fitting
portion of the load flanks and/or the stabbing flanks of the female
threaded zone from the axis of revolution by a value in the range
0.01 to 0.05 mm.
[0018] The distance of the portion of the load flanks and/or the
stabbing flanks of the male threaded zone from the axis of
revolution differs from the distance of the corresponding portion
of the load flanks and/or the stabbing flanks of the female
threaded zone from the axis of revolution by a value substantially
equal to 0.02 mm.
[0019] The portion of the load flanks and/or the stabbing flanks of
the male and female threaded zones is constituted by two segments
connected together tangentially via a first radius of
curvature.
[0020] The two segments connected together tangentially via a
radius of curvature form an angle in the range 90 to 120
degrees.
[0021] The portion of the load flanks and/or the stabbing flanks of
the male and female threaded zones is connected to the thread crest
and/or root by means of a second radius of curvature.
[0022] The portion of the load flanks and/or the stabbing flanks of
the male and female threaded zones is a continuous curve provided
with a point of inflection, said curve being connected tangentially
to the thread crest and to the root.
[0023] The threaded zones each have a taper generatrix forming an
angle .beta. with the axis of revolution of the tubular
components.
[0024] The thread crests and roots are parallel to the axis of the
tubular component.
[0025] The invention also concerns a threaded connection resulting
from connecting a set in accordance with the invention by
make-up.
[0026] In accordance with certain characteristics, the male and
female ends of the connection each respectively comprise a sealing
surface which can cooperate with each other in tightening contact
when the portions of the threaded zones cooperate following
self-locking make-up.
[0027] In accordance with other characteristics, the threaded
connection is a threaded connection of a drilling component.
[0028] The characteristics and advantages of the invention are set
out in more detail in the following description, made with
reference to the accompanying drawings.
[0029] FIG. 1A is a diagrammatic view in longitudinal section of a
connection resulting from coupling two tubular components by
self-locking make-up in accordance with one embodiment of the
invention.
[0030] FIG. 1B is a diagrammatic view in longitudinal section of a
male tubular component in accordance with one embodiment of the
invention.
[0031] FIG. 1C is a diagrammatic view in longitudinal section of a
female tubular component in accordance with one embodiment of the
invention.
[0032] FIG. 2 is a detailed diagrammatic view in longitudinal
section of threaded zones of the connection of FIG. 1.
[0033] FIGS. 3a, 3b, 3c, 3d, 3e and 3f are each detailed
longitudinal sectional views of male and female threads in
accordance with particular embodiments of the invention.
[0034] FIG. 4 is a detailed view of the particular embodiment shown
in FIG. 3a.
[0035] FIG. 6a shows a make-up curve corresponding to make-up of a
prior art connection.
[0036] FIG. 6b shows a make-up curve corresponding to make-up of a
connection in accordance with an embodiment of the invention.
[0037] The threaded connection shown in FIG. 1A and with axis of
revolution 10 comprises, in known manner, a first tubular component
with the same axis of revolution 10 provided with a male end 1 and
a second tubular component with the same axis of revolution 10
provided with a female end 2.
[0038] The tubular components shown respectively in FIGS. 1B and 1C
each comprise ends 1 and 2, in known manner. Said ends each finish
in a terminal surface 7, 8 which is orientated radially with
respect to the axis 10 of the threaded connection, and are
respectively provided with threaded zones 3 and 4 which cooperate
together for mutual connection of the two elements by make-up. The
threaded zones 3 and 4 are of known type known as "self-locking"
(also said to have a progressive variation of the axial width of
the threads and/or the intervals between threads), such that
progressive axial tightening occurs during make-up until a final
locking position is reached.
[0039] In known manner and as can be seen in FIG. 2, the term
"self-locking threaded zones" means threaded zones including the
features detailed below. The flanks of the male threads (or teeth)
32, like the flanks of the female threads (or teeth) 42, have a
constant lead while the width of the threads decreases in the
direction of the respective terminal surfaces 7, 8, such that
during make-up the male 32 and female 42 threads (or teeth) finish
by locking into each other in a predetermined position. More
precisely, the lead LFPb between the load flanks 40 of the female
threaded zone 4 is constant, as is the lead SFPb between the
stabbing flanks 41 of the female threaded zone, wherein in
particular the lead between the load flanks 40 is greater than the
lead between the stabbing flanks 41.
[0040] Similarly, the lead SFPp between the male stabbing flanks 31
is constant, as is the lead LFPp between the male load flanks 30.
Further, the respective leads SFPp and SFPb between the male 31 and
female 41 stabbing flanks are equal to each other and are smaller
than the respective leads LFPp and LFPb between the male 30 and
female 40 load flanks, which are also equal to each other.
[0041] As can be seen in FIG. 2, and as is known in the art, the
male and female threads (or teeth) have a profile, viewed in
longitudinal section passing through the axis of the threaded
connection 10, which has the general appearance of a dovetail such
that they are solidly fitted one into the other after make-up. This
additional guarantee means that risks known as "jump-out",
corresponding to the male and female threads coming apart when the
connection is subjected to large bending or tensile loads, are
avoided. More precisely, the geometry of the dovetail threads
increases the radial rigidity of their connection compared with
threads which are generally termed "trapezoidal" with an axial
width which reduces from the base to the crest of the threads.
[0042] Advantageously and as can be seen in FIG. 2, the threadings
3 and 4 of the tubular components are orientated along a taper
generatrix 20 so as to facilitate the progress of make-up. In
general, this taper generatrix forms an angle with the axis 10
which is included in a range from 1 degree to 5 degrees. In the
present case, the taper generatrix is defined as passing through
the middle of the load flanks.
[0043] Advantageously and as can be seen in FIG. 2, the crests of
the teeth and the roots of the male and female threaded zones are
parallel to the axis 10 of the threaded connection. This
facilitates machining.
[0044] FIGS. 3a, 3b, 3c, 3d, 3e, 3f, 4 and 5 each show a
longitudinal sectional view of a male thread 32 and a female thread
42 each belonging to a tubular component. These tubular components
constitute a set in accordance with the invention. Each of the
Figures shows the profiles of the male 31 and female 41 stabbing
flanks viewed along a longitudinal section passing through the axis
of revolution 10 of the tubular components. This axis is also the
axis of revolution of the connection. In accordance with the
invention, the profile of the male 31 stabbing flanks and the
profile of the female 41 stabbing flanks each has an identical
portion E, E'. More precisely, these portions are identical such
that from a graphical viewpoint, they can be superimposed one on
the other.
[0045] Further, the male and female threads can be fitted one into
the other over these identical portions E, E' when the tubular
components are made up one into the other. The term "fitted" means
that the identical portions have a certain convexity and/or a
certain concavity such that they are complementary and they can be
fitted one into the other. This means that when the flanks (load or
stabbing) of the corresponding male and female threads (also known
as teeth) are fitted one against the other, said threads can no
longer translate with respect to each other along an axis
perpendicular to the axis of revolution 10.
[0046] Again in accordance with the invention, the distance d of
the portion E of the profile of the stabbing flanks of the male
threaded zone from the axis of revolution 10 is different from the
distance d' of the portion E' of the profile of the stabbing flanks
of the female threaded zone from the axis of revolution 10. For
this reason, the portions E and E' are offset with respect to each
other radially, i.e. with respect to the axis of revolution 10. The
term "distance d of the portion E from the axis of revolution 10"
means the separation of said portion from the axis of revolution
10. In other words, the portions E and E' can be fitted one into
the other but do not face each other. In order to fit them one into
the other it is not sufficient to carry out a translation from the
axis of revolution 10. In addition, a translation along an axis
perpendicular to the axis of revolution 10 must be carried out.
[0047] According to the embodiments shown in FIGS. 3a, 3b, 3c, 3d,
3e, 3f and 4, the distance d of the portion E of the profile of the
stabbing flank of the male threaded zone from the axis of
revolution 10 is less than the distance d' of the portion E' of the
profile of the stabbing flanks of the female threaded zone from the
axis of revolution 10.
[0048] According to the embodiment shown in FIG. 5, the distance d
of the portion E of the profile of the stabbing flanks of the male
threaded zone from the axis of revolution 10 is greater than the
distance d' of the portion E' of the profile of the stabbing flanks
of the female threaded zone with respect to the axis of revolution
10.
[0049] According to the embodiments shown in FIGS. 3a, 3b, 3c, 3d,
3e, 3f and 4, the identical portions E, E' are offset with respect
to each other radially along an axis perpendicular to the axis of
revolution 10. Thus, during make-up, the thread crests do not
interfere with the thread roots. They may also exhibit a certain
clearance. In contrast, when the male and female flanks lock one
against the other at the end of make-up, the clearance due to the
offset of the identical portions tends to be reduced to cancel out
under the final make-up force. This means that the initially offset
identical portions E and E' are brought face to face and finish by
being pressed one against the other. At the same time, the roots
and crests of the male and female threads are also pressed against
one another under the effect of elastic deformations. Depending on
the magnitude of the initial clearance present between the thread
roots and thread crests, at the end of make-up, thread roots and
crests may be in contact under pressures which may be large or
small. The tightness of the threading is thus ensured by the fact
that the male and female threads are in tightening contact at the
load flanks, the stabbing flanks and at the thread crests and
roots.
[0050] In the embodiment shown in FIG. 5, the thread crests are in
contact with the thread roots at a contact pressure which is
selected so as to avoid galling. In contrast, when the initially
offset identical portions E and E' are brought face to face to
finish by being pressed against each other, the roots and crests of
the male and female threads remain pressed against each other under
a conserved contact pressure.
[0051] In all cases and regardless of the embodiment of the
invention, elastic deformation of the male and/or female flank
profiles occurs such that the profile of the male flanks and the
profile of the female flanks are different from each other before
make-up and match each other after make-up. The tightness of the
threading is ensured by the fact that at the end of make-up, the
male and female threads are in tightening contact at the load
flanks, the stabbing flanks and at the thread crests and roots.
[0052] FIG. 6A shows a make-up curve for a conventional
self-locking radial tightening threading. It appears that the
variation in the torque applied during make-up at the thread roots
and crests is almost zero (see curve D), while the variation in the
torque applied during make-up at the load flanks and at the
stabbing flanks (see curves C and B) increases. Clearly, the
variation in the torque applied during make-up at the threaded zone
taken as a whole also increases (see curve A), this latter being
taken up, in a conventional manner, by the stabbing flanks and more
particularly by the load flanks.
[0053] In contrast, in the case of a self-locking radial tightening
threading in accordance with an embodiment of the invention, it
appears that the variation in the torque applied during make-up at
the thread crests and roots has a peak (see curve D, FIG. 6B),
which corresponds to the force for fitting the identical portions E
and E' one into the other. This torque returns to almost zero at
the end of make-up so that the total torque is taken up by the
stabbing flanks and more particularly by the load flanks.
[0054] Advantageously, the distance d of the portion E of the
profile of the stabbing flanks of the male threaded zone from the
axis of revolution 10 differs from the distance d' of the portion
E' of the profile of the stabbing flanks of the female threaded
zone from the axis of revolution 10 by a value e in the range 0.01
to 0.05 mm. Thus, the final make-up force which allows complete
fitting of the male and female flanks is in the range 15% to 30% of
the maximum applicable force.
[0055] Preferably again, the distance d of the portion E of the
profile of the stabbing flanks of the male threaded zone from the
axis of revolution 10 differs from the distance d' of the portion
E' of the profile of the stabbing flanks of the female threaded
zone from the axis of revolution 10 by a value e which is
substantially equal to 0.02 mm. This means that the thread
crest/root contact can be optimized without reaching the
plastification limit of the material.
[0056] According to an advantageous embodiment described in FIG. 3a
and detailed in FIG. 4, the portions E, E' of the profiles of the
stabbing flanks of the male and female threaded zones are
constituted by two segments S connected together tangentially via a
radius of curvature R. This means that the portions of the flanks
which can be fitted one into the other are inclined planar surfaces
which act as a ramp, facilitating fitting of the flanks one into
the other. The tangential connection by means of a radius of
curvature R means that sharp angles, which are seats of stress
concentrations, can be avoided.
[0057] Advantageously, the two segments which are tangentially
connected via a radius of curvature form an angle in the range 90
to 120 degrees. This range of values means that a profile can be
obtained with a convexity, or respectively concavity, of the male
flanks, respectively the female flanks, is controlled. This enables
to optimize the fatigue strength of connections which are subjected
to bending and tension/compression stresses. This means that
engagement and disengagement of the male and female elements is
facilitated.
[0058] Advantageously, the identical portions E, E' of the profiles
of the stabbing flanks of the male and female threaded zones are
connected to the thread crest 35, 45 and to the thread root 36, 46
via a radius of curvature r, also in order to avoid sharp
angles.
[0059] In accordance with another embodiment detailed in FIG. 3b,
the identical portions E, E' of the stabbing flanks of the male and
female threaded zones are also two segments connected together
tangentially via a radius of curvature, the segments being
substantially equal in length.
[0060] In accordance with two other similar embodiments detailed in
FIGS. 3c and 3d, the identical portions E, E' of the stabbing
flanks of the male and female threaded zones comprise one or more
bulges which allow adjustable fitting of the profiles as a function
of the dimension of the bulge.
[0061] In accordance with another embodiment detailed in FIG. 3e,
the identical portions E, E' of the stabbing flanks of the male and
female threaded zones are a continuous curve with no singular point
and provided with a point of inflection. Preferably, as explained
above, said curve is connected tangentially to the thread crest and
root by means of a radius of curvature.
[0062] The embodiment shown in FIG. 3f is a mode which is similar
to that shown in FIG. 3a. In this mode, the function of the ramp of
segments S is reinforced.
[0063] Advantageously and as can be seen in FIG. 1, the fluid-tight
seal, both towards the interior of the tubular connection and the
external medium, may be reinforced by two sealing zones 5, 6
located close to the terminal surface 7 of the male element.
[0064] It is necessary to guarantee a higher degree of tightness
corresponding to high pressures at the connection between two
components. To this end, in other types of connections such as the
YAM.RTM. TOP connections described by the Applicant in catalogue no
940, it is known to provide a sealing surface intended to cooperate
in a radial tightening with a sealing surface provided on the
female end of the connection on the male end of the connection
beyond the threaded zone.
[0065] The sealing zone 5 may have a domed surface which is turned
radially outwardly, with a diameter which decreases towards the
terminal surface 7. The radius of this domed surface is preferably
in the range 30 to 100 mm. Too high a radius (>150 mm) of the
domed surface induces disadvantages which are identical to those of
cone-on-cone contact. Too small a radius (<30 mm) of this domed
surface induces an insufficient contact width.
[0066] Facing this domed surface, the female end 2 has a tapered
surface which is turned radially inwardly with a diameter which
also decreases in the direction of the terminal surface 7 of the
male element. The tangent of the peak half angle of the tapered
surface is in the range 0.025 to 0.075, i.e. a taper in the range
5% to 15%. Too low a taper (<5%) for the tapered surface induces
a risk of galling on make-up and too high a taper (>15%)
necessitates very tight machining tolerances.
[0067] The inventors have discovered that such a contact zone
between a tapered surface and a domed surface enables to produce a
high effective axial contact width and a substantially
semi-elliptical distribution of contact pressures along the
effective contact zone, in contrast to contact zones between two
tapered surfaces which have two narrow effective contact zones at
the ends of the contact zone.
[0068] It should be noted that the sealing zones 5 and 6 of the
male and female end may be disposed close to the terminal surface 8
of the female end.
[0069] It should be noted that the invention may also be applied to
the load flanks and not simply to the stabbing flanks. Similarly,
the invention may be applied to only a portion of the stabbing
flanks or to only a portion of the load flanks. This has the
advantage of reducing the final make-up force, but also has the
disadvantage of reducing the tightness of the connection. In
accordance with the invention, it is at the end of make-up that the
clearances which still exist between the male and female flanks and
between the corresponding thread roots and crests disappear
completely. At this moment the connection is sealed.
[0070] The invention has a further advantage of providing optimized
management of the flows of lubricants used to facilitate make-up.
The fact that clearances are retained at the thread flanks until
the very end of make-up means that lubricant can move more
uniformly over the threaded zones. This also avoids trapping of the
lubricant in the threaded zones.
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